Flexible couplings for mechanical power transmissions

ABSTRACT

A flexible coupling includes a flexible diaphragm body having a first end and a second end. A member is fixed to the first end of the flexible diaphragm body. A splined member is fixed to the second end of the flexible diaphragm body. The splined member is configured to shift relative to a rotatable member rotatably fixed thereto in response to axial displacement of rotatable members interconnected by the flexible coupling. The ratio of inner diameter to the outer diameter is selected to allow for packaging the flexible coupling in a confined space.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present disclosure relates to mechanical power transmissions, andmore particularly to flexible couplings for mechanical powertransmission systems.

2. Description of Related Art

Mechanical power transmissions such as in aircraft commonly employinterconnected driving and driven shafts to actuate devices such aswing-mounted slats and slats for controlling flight. Because there canbe angular misalignment and/or axial offsets between interconnecteddriving and driven shafts, some transmissions employ flexible couplingsto accommodate angular misalignment and axial offset between the drivingand driven shafts. Examples of such flexible couplings include universaljoints, gear couplings, and disk couplings.

Universal joints can accommodate large ranges of angular misalignment,but generally have limited capability to accommodate axial mismatch.Gear couplings can accommodate large ranges of axial mismatch, buttypically have limited capability to accommodate angular misalignment.Universal joints and gear couplings generally employ contacting surfacesthat require lubrication and are typically considered to be wear parts,requiring periodic replacement in some applications. Disk couplings,while not requiring lubrication, are generally able to toleraterelatively lesser amounts of angular misalignment and axial mismatchbetween driving and driven shafts.

Such conventional methods and systems have generally been consideredsatisfactory for their intended purpose. However, there is still a needin the art for improved flexible couplings. The present disclosureprovides a solution for this need.

SUMMARY OF THE INVENTION

A flexible coupling includes a flexible diaphragm body having a firstend and a second end. A member is fixed to the first end of the flexiblediaphragm body. A splined member is fixed to the second end of theflexible diaphragm body. The splined member is configured to shiftrelative to a rotatable member rotatably fixed thereto in response toaxial displacement of rotatable members interconnected by the flexiblecoupling.

In certain embodiments, the member can have a flange. The splined membercan have a spline. The splined member can have a flange extending aboutthe splined member. The flange can be disposed between the splinestructure and the flexible diaphragm body. The flexible diaphragm bodycan have two or more diaphragm disks axially spaced between the memberand the splined member. Axially adjacent diaphragm disks of the flexiblediaphragm body can be fixed to one another at their outer peripheries.Axially adjacent diaphragm disks of the flexible diaphragm body can befixed to one another at their inner peripheries.

In accordance with certain embodiments, the flexible coupling can befrictionless. The flexible coupling can have an open through-boreextending continuously between opposed ends of the flexible diaphragmbody. The open through-bore can extend continuously between oppositeends of the flexible diaphragm body and the member. The openthrough-bore can extend continuously between opposite ends of theflexible diaphragm body and the splined member. The open through-borecan extend continuously between opposite ends of the splined member andthe member.

It is also contemplated that, in accordance with certain embodiments,the flexible diaphragm body can have an inner diameter that is greaterthan an outer diameter of the splined member. The flexible diaphragmbody can have an inner diameter that is greater than an inner diameterof the splined member. The flexible diaphragm body can have innerdiameter that is greater than an inner diameter of the member. Theflexible diaphragm body can have an outer diameter that is less thanabout four and half times an inner diameter of the flexible diaphragmbody.

A mechanical power transmission for a flight control surface actuatorincludes a flexible coupling as described above. A first rotatablemember is fixed axially and is fixed in rotation relative to the member.A second rotatable member is fixed in rotation and axially free relativeto the splined member. The splined member can be movable between a firstaxial offset and a second axial offset relative to the second rotatablemember, the second axial offset being greater than the first axialoffset to reduce equivalent cyclic stress in the flexible diaphragmbody. In certain embodiments, a flight control surface can operablyconnected to the flexible coupling by one of the first and secondrotatable members. In accordance with certain embodiments, a source ofmechanical rotation can be connected to flexible coupling by one of thefirst and second rotatable members.

A method transmitting torque through a flexible coupling includesapplying axial force to a flexible coupling by axially displacingrotatable members interconnected by the flexible coupling. The axialforce is reducing by axially shifting an end of the flexible couplingrelative to one of the interconnected rotatable members. Equivalentcyclic stress in the flexible diaphragm body can also be reduced byaxially shifting the end of the flexible coupling relative to the one ofthe interconnected rotatable members.

These and other features of the systems and methods of the subjectdisclosure will become more readily apparent to those skilled in the artfrom the following detailed description of the preferred embodimentstaken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

So that those skilled in the art to which the subject disclosureappertains will readily understand how to make and use the devices andmethods of the subject disclosure without undue experimentation,embodiments thereof will be described in detail herein below withreference to certain figures, wherein:

FIG. 1 is a schematic view of an exemplary embodiment of a mechanicalpower transmission constructed in accordance with the presentdisclosure, showing flight control device operably connected to a sourceof mechanical rotation by a flexible coupling;

FIG. 2 is schematic view of the mechanical power transmission of FIG. 1,showing the flexible coupling communicating torque while accommodatingangular misalignment and axial offset between rotatable membersinterconnected by the flexible coupling;

FIG. 3 is a side elevation view of the flexible coupling of FIG. 1,showing a splined member and a flanged member of the flexible couplingfixed to opposed first and second ends of a flexible diaphragm body;

FIG. 4 is a cross-section view of the flexible coupling of FIG. 1,showing a through-bore extending continuously through an interior of theflexible coupling;

FIG. 5 is a diagram of a method of communicating torque through amechanical power transmission, showing steps of the method; and

FIGS. 6A and 6B are charts of equivalent cyclic stress and axial forceas functions of axial displacement, showing reduction in the axial forceand equivalent cyclic stress with axial shift of an end of the flexiblerelative to a rotatable member rotatably fixed to the end, respectively.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made to the drawings wherein like referencenumerals identify similar structural features or aspects of the subjectdisclosure. For purposes of explanation and illustration, and notlimitation, a partial view of an exemplary embodiment of a flexiblecoupling in accordance with the disclosure is shown in FIG. 1 and isdesignated generally by reference character 100. Other embodiments offlexible couplings, mechanical power transmissions, and methods ofcommunicating torque through flexible couplings in accordance with thepresent disclosure, or aspects thereof, are provided in FIGS. 2-6, aswill be described. The systems and methods described herein can be usedfor actuating flight control surfaces in aircraft, though the presentdisclosure is not limited to flight control surface actuation or toaircraft in general.

Referring to FIG. 1, an aircraft 10 is shown. Aircraft 10 includes aflight control surface 12 operably connected to a source of mechanicalrotation 14 by a mechanical power transmission 16. Flight control device12 includes, by way of non-limiting example, a slat or a flap flightcontrol surface for controlling attitude of aircraft 10 during flight.Source of mechanical rotation 14 includes, by way of non-limitingexample, an electric motor or a power-take-off shaft, and is remotelyconnected to mechanical power transmission 16.

Mechanical power transmission 16 includes a first rotatable member 18, asecond rotatable member 20, and flexible coupling 100. Mechanical powertransmission 16 is rotatably supported relative to aircraft 10 by afirst bearing structure 22 and a second bearing structure 24. Firstrotatable member 18 and second rotatable member 20 are interconnected byflexible coupling 100, first rotatable member 18 being and rotatablysupported within first bearing structure 22 and second rotatable member20 being and rotatably supported within second bearing structure 24.

With reference to FIGS. 2, flexible coupling 100 of mechanical powertransmission 16 is shown. Flexible coupling 100 includes a flexiblediaphragm body 102 having a first end 104 and a second end 106, a member108, and a splined member 110. Member 108 is fixed to first end 104 offlexible diaphragm body 102. Splined member 110 is fixed to second end106 of flexible diaphragm body 102. Splined member 110 is configured toaxially shift between a first axial offset 36 and a second axial offset38 relative to second rotatable member 20 in response to axialdisplacement of first rotatable member 18 and/or second rotatable member20, which are interconnected by flexible coupling 100.

First rotatable member 18 defines a first rotation axis 26 and is fixedboth rotatably and axially relative to member 108. Second rotatablemember 20 defines a second rotation axis 28, is rotatably fixed relativeto splined member 110, and is axially free relative to splined member110. First rotation axis 26 is angled relative to second rotation axis28, thereby defining an angular misalignment 34 between first rotatablemember 18 and second rotatably member 20. Second rotatable member 20 isaxially offset relative to first rotatable member by a first axialoffset 36, which may be a nominal axial offset between the elements.

Because both first rotatable member 18 and second rotatable member 20are rotatably fixed to flexible coupling 100, torque T applied to eitherof first rotatable member 18 and second rotatable member 20 iscommunicated through flexible coupling 100 to the other of firstrotatable member 18 and second rotatable member 20. Flexible diaphragmbody 102 is configured to accommodate one or more torque T, angularmisalignment 34, and/or a range of axial offsets defined between firstaxial offset 36 and second axial offset 38 by deformation, shownschematically in FIG. 2 with bowing of flexible diaphragm body 102. Oneor more of torque T, angular misalignment 34, and the a range of axialoffsets defined between first axial offset 36 and second axial offset 38generate equivalent a cyclic stress 42. Equivalent cyclic stress 42 isborn by flexible diaphragm body 102 and is kept below the endurancestrength of the material forming flexible diaphragm body 102, in part,by the axial width selected for flexible diaphragm body 102.

As will be appreciated by those of skill in the art in view of thepresent disclosure, vehicles such as aircraft 10 are commonly subject tofactors such as flights loads, thermal effects, and/or variation in theamount of torque communicated between interconnected rotatable members.With respect to mechanical power transmission 16, one or more theseexemplary factors exert a force 30 (shown in FIG. 1) on mechanical powertransmission 16. Force 30 in turn exerts an axial force component 44along mechanical power transmission 16, axial force component 44 beingsufficient to axially displace mechanical power transmission 16, orelements thereof, axially. Axial displacement of mechanical powertransmission 16, or elements thereof, exerts axial force component 44 onflexible coupling 100, increasing the level equivalent cyclic stress 42born by flexible diaphragm body 102 for a given axial width of flexiblediaphragm body 102.

As will also be appreciated by those of skill in the art in view of thepresent disclosure, the force born by flexible couplings generallyinfluences the axial width of the flexible coupling structure, largerforces typically requiring larger axial widths. In applications such asflight control actuation mechanical drive systems, where space can belimited, there may be insufficient space for the outside widths (oradditional axially stacked diaphragm disks) necessary to bear the cyclicequivalent stress with such applications, excluding the use of diaphragmdisc couplings.

In embodiments described herein, splined member 110 is configured toaxially shift relative to second rotatable member 20. In this respectsplined member 110 is configured to axially shift between first axialoffset 36 and second axial offset 38 when axial force component 44exceeds a predetermined threshold force level. Axially shifting betweenfirst axial offset 36 and second axial offset 38, or axial takeup eventsreduces axial force component 44 and reduces commensurately theequivalent cyclic stress 42 born by flexible diaphragm body 102.Reducing the equivalent cyclic stress 42 born by flexible diaphragm body102 reduces the axial width of flexible diaphragm body 102, e.g.,diameter D (shown in FIG. 4). The reduction in the axial width can besuch that flexible diaphragm body 102 can be arranged within the limitedspace of an aircraft wing or similarly restrictive structure, enablinguse of flexible coupling 100 in such applications. In embodiments,flexible diaphragm body 102 may have an outside diameter that is betweenabout two (2) and about five (5) inches. This enables flexible coupling100 to be packaged within the confines of an aircraft wing structure. Incertain embodiments outer diameter D of flexible diaphragm 102 is aboutthree (3) inches.

With reference to FIG. 3, flexible coupling 100 is shown. Member 108 hasa flange 122 disposed on an end of member 108 opposite flexiblediaphragm body 102. Flange 122 is configured to connect first rotatablemember 18 (shown in FIG. 2) to flexible coupling 100. Flange 122 mayinclude a fastener pattern 112 for fixing member 108 both axially and inrotation relative to first rotatable member 18. A first fused joint 114is disposed on an end of member 108 axially opposite flange 122. Firstfused joint 114 fixes member 108 to flexible diaphragm body 102 and caninclude a weld or a plurality of interfused layers formed with anadditive manufacturing technique.

Splined member 110 includes a plurality of longitudinal splinestructures 120 defined on an end 118 of splined member 110 oppositeflexible diaphragm body 102. Spline structures 120 are configured toretain splined member 110 in an axially free disposition relative tosecond rotatable member 20 (shown in FIG. 2). A flange 148 extends aboutsplined member 110, flange 148 being axially spaced between splinestructures 120 and flexible diaphragm body 102. Flange 148 comprises astore of sacrificial material for dynamically balancing flexiblecoupling 100. Flange 148 may also form an axial stop, flange 148restricting axial shift of splined member 110 relative to secondrotatable member 20. A second fused joint 116 is disposed on an end ofmember 108 axially opposite flange 122. Second fused joint 116 issimilar to first fused joint 114, and additionally fixes splined member110 to flexible diaphragm body 102.

Flexible diaphragm body 102 includes a first diaphragm disk 124, asecond diaphragm disk 126, a third diaphragm disk 128, and a fourthdiaphragm disk 130 axially stacked between member 108 and splined member110. First diaphragm disk 124 has a radially inner periphery 132 and aradially outer periphery 134. Second diaphragm disk 126 has a radiallyinner periphery 138 and a radially outer periphery 136. Third diaphragmdisk 128 has a radially inner periphery 140 and a radially outerperiphery 142. Fourth diaphragm disk 130 has a radially inner periphery144 and a radially outer periphery 146.

First diaphragm disk 124 is axially adjacent to second diaphragm disk126. First diaphragm disk 124 is connected to member 108 at its radiallyinner periphery 132. Radially outer periphery 134 of first diaphragmdisk 124 is in turn connected to radially outer periphery 136 of seconddiaphragm disk 126.

Second diaphragm disk 126 is axially adjacent to third diaphragm disk128. Inner periphery 138 of second diaphragm disk 126 is connected toradially inner periphery 140 of third diaphragm disk 128. Thirddiaphragm disk 128 is axially stacked between second diaphragm disk 126and fourth diaphragm disk 130, radially outer periphery 142 of thirddiaphragm disk 128 being connected to radially outer periphery 146 offourth diaphragm disk 130. Radially inner periphery 144 of fourthdiaphragm disk 130 is in turn connected to splined member 110. Althoughillustrated as having four diaphragm members, it is to be understood andappreciated that embodiments of flexible coupling described herein canhave fewer than four diaphragm disks or more than four diaphragm disks,as suitable for an intended application.

With reference to FIG. 4, flexible coupling 100 is shown. Flexiblecoupling 100 has an interior 158 defining an open through-bore 154. Openthrough-bore 154 extends continuously between first end 104 (shown inFIG. 2) and second end 106 (shown in FIG. 2) of flexible diaphragm body102, and is empty. In this respect flexible diaphragm body 102 isaxially unlimited, deformation and shift being dictated by elementsexternal to flexible coupling 100.

It is contemplated that open through-bore 154 extend continuouslybetween second 106 of the flexible diaphragm body 102 and an end ofmember 108 opposite flexible diaphragm body 102. In certain embodimentsopen through-bore 154 extends continuously between first end 104 offlexible diaphragm body 102 and an end of splined member 110 oppositeflexible diaphragm body 102. In the illustrated exemplary embodiment,open through-bore 154 extends continuously between axially oppositeends of flexible coupling 100, i.e. between ends of member 108 andsplined member 110 disposed on axially opposite sides of flexiblediaphragm body 102. In this respect the illustrated exemplary embodimentof flexible coupling 100 is frictionless, there being no slidingsurfaces disposed within open through-bore 154. This reduces wear withinflexible coupling 100, potentially extending the service life offlexible coupling 100.

Splined member 110 has an inner diameter A and an outer diameter B.Flexible diaphragm body 102 has an inner diameter C and outer diameterD. Member 108 has an inner diameter E and an outer diameter F. Outerdiameter D of flexible diaphragm body 102 is less than about 4.7 timesinner diameter C, and in certain embodiments outer diameter D offlexible diaphragm body 102 is less than about 4.5 times inner diameterC. Sizing outer diameter D such that outer diameter D is less than about4.7 times inner diameter C enables flexible coupling 100 to transfersufficient torque for a flight control actuation system and bearequivalent cyclic stress 42, as supplemented by axial force component 44from axial displacement of rotatable members of the flight controlactuation system—within the confines of an aircraft wing.

In the illustrated exemplary embodiment, inner diameter C of flexiblediaphragm body 102 is greater than inner diameter A of splined member110. Optionally, inner diameter C of flexible diaphragm body 102 is alsogreater than inner diameter E of member 108, thereby providing apiloting structure to facilitate assembly of flexible coupling 100.Sizing the respective inner and outer diameters of flexible coupling 100also allows for outer diameter D of flexible diaphragm body 102 to berelatively small, allowing flexible coupling 100 to be arranged withinthe confines of an aircraft wing structure.

The plurality of diaphragm disks, e.g., a first diaphragm disk 124, asecond diaphragm disk 126, a third diaphragm disk 128, and fourthdiaphragm disk 130, define respective tapered profiles 150. Taperedprofiles 150 extend between respective inner peripheries and outerperipheries of diaphragm disks 124-130. It is contemplated that taperedprofiles 150 are as described in U.S. Pat. No. 8,591,345 to Stocco etal. (Stocco), issued on Nov. 26, 2013, the contents of which isincorporated herein by reference. In certain embodiments, taperedprofiles are similar to those described with Stocco, with the differencethat the ratio of outer diameter D to inner diameter C is reduced.

With reference to FIG. 5, a method 200 of transmitting torque through amechanical power transmission is shown, e.g., mechanical powertransmission 16 (shown in FIG. 1). Method 200 includes driving a firstrotatable member, e.g., first rotatable member 18 (shown in FIG. 1),with a second rotatable member, e.g., second rotatable member 20 (shownin FIG. 1), as shown with box 210. Method 200 also includes axiallydisplacing one or more components of the mechanical power transmission,as shown with box 220. The axial displacement exerts an axial force,e.g., axial force component 44 (shown in FIG. 2), on a flexiblecoupling, e.g., flexible coupling 100 (shown in FIG. 1) interconnectingthe rotatable members, as shown with box 230. Responsive to the axialforce, an end of the flexible coupling, e.g., splined end 108 (shown inFIG. 2), is displaced relative to a rotatable member connected thereto,as shown in box 240. The axial displacement reduces the axial forcecomponent exerted on the flexible coupling, as shown with box 242. Theaxial displacement also reduced the equivalent cyclic stress, e.g.,equivalent cyclic stress 42 (shown in FIG. 2), born by the flexiblecoupling, as shown with box 244.

With reference to FIGS. 6A and 6B, the corresponding increase isequivalent cyclic stress 42 (shown in FIG. 2) born by flexible diaphragmbody 102 is offset by axial shift 40. This reduces the axial forcecomponent 44 (shown in FIG. 2) and equivalent cyclic stress 42 born byflexible diaphragm body 102 prior to equivalent cyclic stress 42exceeding the endurance strength of the material from which flexiblediaphragm body 102 is constructed. Reduction in equivalent cyclic stress42 associated with axial shift 40 is shown in FIG. 6A. Reduction inforce 44 associated with axial shift 40 is shown in FIG. 6B.

The methods and systems of the present disclosure, as described aboveand shown in the drawings, provide for flexible couplings with superiorproperties including a self-limiting stress relief mechanism and aradially compact arrangement. While the apparatus and methods of thesubject disclosure have been shown and described with reference topreferred embodiments, those skilled in the art will readily appreciatethat changes and/or modifications may be made thereto without departingfrom the scope of the subject disclosure.

What is claimed is:
 1. A flexible coupling, comprising: a flexiblediaphragm body having a first end and a second end; a member fixed tothe first end of the flexible diaphragm body; and a splined member fixedto the second end of the flexible diaphragm body, wherein the splinedmember is configured to axially shift relative to a first rotatablemember rotatably fixed to the splined member in response to axialdisplacement of the first rotatable member relative to a secondrotatable member interconnected to the first rotatable member by theflexible coupling while transmitting torque between the first rotatablemember and the second rotatable member, wherein the flexible diaphragmbody comprises a plurality of diaphragm disks spaced between the memberand the splined member, a first of the plurality of diaphragm disks anda second of the plurality of diaphragm disks fixed to one another attheir inner peripheries, wherein the flexible diaphragm body has aninner diameter that is greater than an inner diameter of the splinedmember.
 2. The flexible coupling as recited in claim 1, wherein themember comprises a flange.
 3. The flexible coupling as recited in claim1, wherein the flexible coupling has an open through-bore extendingcontinuously between opposed ends of the flexible diaphragm body.
 4. Theflexible coupling as recited in claim 1, wherein the flexible couplinghas an open through-bore extending continuously between opposite ends ofthe flexible diaphragm body and the member.
 5. The flexible coupling asrecited in claim 1, wherein the flexible coupling has an openthrough-bore extending continuously between opposite ends of theflexible diaphragm body and the splined member.
 6. The flexible couplingas recited in claim 1, wherein the flexible coupling has an openthrough-bore extending continuously between opposite ends of the splinedmember and the member.
 7. The flexible coupling as recited in claim 1,wherein the splined member defines a flange extending thereabout andarranged axially between a spline structure of the splined member andthe flexible diaphragm body.
 8. The flexible coupling as recited inclaim 1, wherein the flexible coupling is frictionless.
 9. The flexiblecoupling as recited in claim 1, wherein the flexible diaphragm bodycomprises a second plurality of diaphragm disks spaced between themember and the splined member, a first of the second plurality ofdiaphragm disks and a second of the second plurality of diaphragm disksbeing fixed to one another at their outer peripheries.
 10. A flexiblecoupling comprising: a flexible diaphragm body having a first end and asecond end; a member fixed to the first end of the flexible diaphragmbody; and a splined member fixed to the second end of the flexiblediaphragm body, wherein the splined member is configured to axiallyshift relative to a first rotatable member rotatably fixed to thesplined member in response to axial displacement of the first rotatablemember relative to a second rotatable member interconnected to the firstrotatable member by the flexible coupling while transmitting torquebetween the first rotatable member and the second rotatable member,wherein the flexible diaphragm body comprises a plurality of diaphragmdisks spaced between the member and the splined member, a first of theplurality of diaphragm disks and a second of the plurality of diaphragmdisks fixed to one another at their inner peripheries, wherein theflexible diaphragm body has an inner diameter that is greater than aninner diameter of the member.
 11. A flexible coupling as comprising: aflexible diaphragm body having a first end and a second end; a memberfixed to the first end of the flexible diaphragm body; and a splinedmember fixed to the second end of the flexible diaphragm body, whereinthe splined member is configured to axially shift relative to a firstrotatable member rotatably fixed to the splined member in response toaxial displacement of the first rotatable member relative to a secondrotatable member interconnected to the first rotatable member by theflexible coupling while transmitting torque between the first rotatablemember and the second rotatable member, wherein the flexible diaphragmbody comprises a plurality of diaphragm disks spaced between the memberand the splined member, a first of the plurality of diaphragm disks anda second of the plurality of diaphragm disks fixed to one another attheir inner peripheries, wherein the flexible diaphragm body has anouter diameter and an inner diameter, the outer diameter being less thanabout 4.5 times the inner diameter.